function add(a, b) {
    return a + b
}
  
function sub(a, b) {
    return a - b
}
  
function commonDivision(a, b) {
    while (b !== 0) {
        if (a > b) {
        a = sub(a, b)
        } else {
        b = sub(b, a)
        }
    }
    return a
}


